Roger Bernadina doubled with two outs in the ninth, driving in Bryce Harper for the go-ahead run and the Washington Nationals held on for a 4-3 win over the Boston Red Sox on Sunday, completing a three-game sweep.

Danny Espinosa doubled twice and drove in two runs for the Nationals, who as a franchise had never won at Fenway Park entering the series.

Harper, Washington's rookie phenom, was out of the starting lineup because of tightness in his back. He pinch-hit for Tyler Moore with one out in the top of the ninth and drew a walk from Alfredo Aceves.

Aceves (0-4) struck out Jesus Flores for the second out, but Bernadina doubled to the right-field corner and came all the way from first, sliding safely into home to put the Nationals up 4-3.

Reliever Tom Gorzelanny (2-1) pitched a scoreless eighth and Tyler Clippard closed the game with his third save of the series, striking out Dustin Pedroia to end it.

Boston manager Bobby Valentine stormed out of the dugout during Pedroia's at-bat to argue a strike and was quickly ejected by home plate umpire Alan Porter. Valentine argued vehemently well after the ejection and came awfully close to making contact a couple of times before leaving the field.

Shortly after Valentine was ejected, Pedroia went down swinging and the Nationals celebrated the interleague sweep.

The Montreal Expos went 0-6 at Fenway and the Nationals were 0-3 in the iconic ballpark since the franchise's move to Washington.

The Red Sox have lost five of six.

David Ortiz hit his 14th homer of the season for the Red Sox, who couldn't hang on to a 2-1 lead. Espinosa hit a two-out double with two runners on in the seventh, putting Washington up 3-2.

Boston tied it in the bottom half after Ryan Sweeney and Nick Punto hit back-to-back singles to start the inning, but Sweeney was the only one to score, coming home on a fielder's choice by Scott Podsednik.

Notes: Daniel Nava was a late scratch from the Red Sox lineup with a sore left hand. Darnell McDonald replaced Nava in left field and Podsednik moved up to the leadoff spot in his place. ... The Red Sox head to Miami for a three-game series with the Marlins, starting Monday. The Nationals will continue on their journey through the AL East with a trip to Toronto for three games against the Blue Jays.